1. Field of the Invention
The invention relates in general to a semiconductor light emitting structure, and more particularly to a semiconductor light emitting structure with better electron restricting ability.
2. Description of the Related Art
Light emitting diode (LED) is a semiconductor light emitting structure which emits a light by converting electric energy into photo energy. Conventional LED includes an epitaxy stacking structure and an upper electrode layer and a lower electrode layer respectively disposed on a top surface and a bottom surface of the epitaxy stacking structure. When electricity is provided to the upper and the lower electrode layer of the LED, the current flows through the epitaxy stacking structure, which releases energy in the form of a light when electrons and electron holes are combined.
The epitaxy stacking structure forms a first semiconductor layer, an active layer and a second semiconductor layer by organic metal chemical vapor deposition (MOCVD) method. Then, a donor and an acceptor are respectively doped into the first semiconductor layer and the second semiconductor layer to form an n-type semiconductor layer carrying negative charges and a p-type semiconductor layer carrying positive charges, so that the LED can transmit currents through the conduction of electrons or electron holes.
In addition, the conventional LED includes an electron blocking layer formed by AlXGa(1-X)N semiconductor material having high energy gap and used for blocking and restricting electrons to be within the active layer, wherein 0≦x≦1. However, when the electron blocking layer is too thick or the Al content of the AlXGa(1-X)N compound is too high, the series resistance of the epitaxy stacking structure will be too high, and a higher bias is required for driving the LED. Besides, the AlXGa(1-X)N semiconductor material has a higher energy gap, making electron holes hard to cross over the electron blocking layer and be transmitted to the active layer. Therefore, the conversion efficiency of the active layer is relatively reduced, and the luminous uniformity of the light emitted by the active layer is poor and needs to be improved.